Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

SA6800
SA6800
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 29th August 2019, 06:07 PM   #1
TNT340 is offline TNT340  United States
diyAudio Member
 
Join Date: Aug 2019
Default SA6800

My original problem was a defective Q3 IC TA 7136P1. I have replaced it twice and it shorts out. I have checked every component related to this IC and compared to the Q4 circuitry. With the IC out of the circuit the other channel works fine and all the voltages are normal. I am using TA 7136P for replacements. Is there something different about the P1 IC. According to pioneer it should be a good replacement.
this is my first post so I hope I am doing it correctly.
  Reply With Quote
Old 29th August 2019, 06:12 PM   #2
rayma is offline rayma  United States
diyAudio Member
 
Join Date: Apr 2011
It would help if you can post the schematic.
  Reply With Quote
Old 29th August 2019, 07:09 PM   #3
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
SA6800
I think that is an opamp which makes it all the stranger as they are usually ultra reliable. Gross over-voltage or reverse polarity supplies are really the only things that will kill them quickly.

Why do you think the opamp is faulty? What is it doing?
  Reply With Quote
Old 29th August 2019, 08:29 PM   #4
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: Maine USA
Pioneer SA-6800 - Manual - Stereo Integrated Amplifier - HiFi Engine

Check the voltages at Q19 Q20; also (carefully!!) at Q1 pins 4 and 7. The stock +/-20V are already quite high for that opamp; if the transistors failed their supply voltage may be MUCH higher. Or if a resistor has burned, it may be Zero, confounding easy diagnosis.
https://cdn.datasheetspdf.com/pdf-do...AP_Toshiba.pdf
  Reply With Quote
Old 29th August 2019, 09:16 PM   #5
TNT340 is offline TNT340  United States
diyAudio Member
 
Join Date: Aug 2019
I switched Q4 from the good channel to the Q3 channel and Q3 is OK now. I think the TA7136P1 is different than the plain Ta 7136P I got. With both Q3 and Q4 out of circuit I get identical voltages and resistance's. I have a cap meter also.
  Reply With Quote
Old 29th August 2019, 09:19 PM   #6
TNT340 is offline TNT340  United States
diyAudio Member
 
Join Date: Aug 2019
The Q4 Channel is OK
  Reply With Quote
Old 30th August 2019, 01:21 AM   #7
TNT340 is offline TNT340  United States
diyAudio Member
 
Join Date: Aug 2019
HI FI Engine has the service manual if you want to look. Having trouble locating the TA7136 P1 IC. Lot of TA7136P and AP.
  Reply With Quote
Old 30th August 2019, 07:33 PM   #8
stocktrader200 is offline stocktrader200  Canada
diyAudio Member
 
Join Date: Jan 2008
Location: Calgary
it's odd that it would short out. That chip has about 3ma of pullup current, much more sink current. voltages should be around 20 - 22v positive and negative. P1 chip may reverse the (+) and (-) signal input pins ensuring it won't work.
This chip is also used in SX-780. I replaced it with 2 6922 triodes, much better.
  Reply With Quote
Old 31st August 2019, 01:30 AM   #9
sgrossklass is offline sgrossklass  Germany
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
The P1 version may be rated at a higher voltage, seeing that the regular TA7136P is only 40 V max and that's how high the supplies are in this amp. (Not uncommon back in the day, e.g. JRC made some +/-22 V rated 4558s which normally are rated +/-18 V max.) Tough. Do verify supply voltages in case there is a shorted regulator pass transistor. The new chips may also be fake.

There has been some discussion on how to replace these ICs in the past. They are early audio opamps with a single-ended output stage. Most manufacturers seem to run them hotter than suggested in the datasheet (the resistor between pins 7 and 5 sets reference current), presumably in an effort to improve distortion performance and voltage noise.

I suppose it would be possible to make an adapter board for one of these, maybe using an NE5534. The pins you are interested in are 2 (+in), 3 (-in), 6 (out), 7 (V+) and 4 (V-). People have, in fact, done so before:
TA7136AP replacement adapter - HOW TO USE - fmtuners
ta7136 substitution - ua726 (TL071 is not too great a match, but NE5534 could be accomodated in a similar manner - make sure you accommodate Cc between pins 5 and 8 depending on gain required, and I would also suggest including maybe 100 nF of rail decoupling between V+ and V- since these chips are fussier about that)
Vintage Audio Upgrades BA312 TA7136 - SparkoS Labs Inc.

I like the idea of using a 5534 (maybe even a 5534A). It is rated +/-22 V max, and with its low input impedance distortion and low current noise (even better in the A series part) would be a good match for the circuit with its somewhat high impedances. At the input levels encountered here its Achilles heel of common-mode distortion won't be relevant either, and circuit gain is so high at 20 dB that external compensation (Cc) may not even be required at all (though the layout won't be great with an adapter and all, so it may still be a good idea to have like 10 pF there). Supply current is likely to be in the same ballpark or even lower than the TA7136 (keep in mind that these are run boosted beyond datasheet levels, current may be doubled for all I can tell, so ~6 mA).

Getting the most out of an opamp like the 5534 will not be possible in this circuit, it would be a major revamp at the very least due to the tone control being involved (read: pots). Probably not worth it. It would be an attractive candidate for the phono preamp though (they are basically made for this - this was the latest and greatest audio opamp design in 1978, and it shows).

Last edited by sgrossklass; 31st August 2019 at 01:40 AM.
  Reply With Quote
Old 31st August 2019, 04:00 AM   #10
TNT340 is offline TNT340  United States
diyAudio Member
 
Join Date: Aug 2019
Default Data sheet

Correct me if I'm wrong but I just looked at the data sheets for the TA7136AP and the P versions. The AP has the same pinout as the SA6800 schematic that has the P1 chip. The P version has pin 2 for input. I have both types on order. Will let you guys know if the AP works.
  Reply With Quote

Reply


SA6800Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


New To Site? Need Help?

All times are GMT. The time now is 06:17 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki